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Schwevers U.,Institute For Angewandte Okologie | Neumann C.,Gasstrasse 18
WasserWirtschaft | Year: 2012

The new fish pass at the northern bank of the Geesthacht dam was built using a double slot pass design, as only this construction type allowed to meet all the required geometric and hydraulic thresholds, recommended by the relevant technical guidelines. Due to the necessity of having to take the European sturgeon as the largest autochthonous species into account, the size of the fish pass has reached dimensions, which are unique in the European region. A further unique feature is the presence of ancillary dotations distributed over the length of the pass. These make it possible to maintain the required minimum flow in the migration corridor, independent of the tidal tailwater level.

Schwevers U.,Institute For Angewandte Okologie | Neumann C.,Knabe Enders Duhrkop Ingenieure GmbH
WasserWirtschaft | Year: 2012

Traceability is a decisive factor for the correct functioning of a fish pass. In the case of the newly built double slot pass at the northern river bank at the weir Geesthacht, this is facilitated by the entrance being located close to the bank, level with the river bed and nearly in line with the adjacent dam. This positioning also avoids any dead ends. Further, five additive spillways in the neighbouring fixed weir segment provide an adequate attraction flow. By supplying varying additional dotation, this attraction flow is independent of tidally induced changes in water level in the tail water.

Adam B.,Institute For Angewandte Okologie | Faller M.,Aussenstelle Des Institute For Angewandte Okologie | Gischkat S.,Aussenstelle Des Institute For Angewandte Okologie | Hufgard H.,Aussenstelle Des Institute For Angewandte Okologie | And 2 more authors.
WasserWirtschaft | Year: 2012

Since the new double slot pass has gone into operation at the Geesthacht dam, an extensive, long term fish-ecological monitoring has been accomplished, which includes the old bypass facility on the southern river bank. Daily counts show that the double slot pass is used by about eight times the number offish as that of the bypass. In addition, the range of species that use the double slot pass is higher than that of the bypass, with 43 and 37 species, respectively. The double slot pass is also used by fish species, which are typical of the River Elbe, such as zander and smelt, but do not appear or are underrepresented in the species range present in the bypass. By implementing transponder technology, important insights are gained into how the traceability of the two fish passes differs, the results often being highly dependent on the respective species. These findings demonstrate that some species prefer ascending the double slot pass, located on the point bank, whilst more powerful swimmers may choose to use the bypass on the cut bank.

So far the experiences with the construction and operation of the Geesthacht double slot pass have been very positive: the considerable effort during the construction has been rewarded with accordingly high fish passages, which strengthens the conclusion that the fish pass is fully functional. However, the question remains, can such an exceptional construction serve as a blueprint for other locations?

As part of the mitigation measures for abstracting cooling water for the coal-fired power plant Moorburg nearby Hamburg, Vattenfall Europe Generation AG was obliged to take measures to protect potentially affected fish species, which have been assigned a high conservation status (FFH species). One of these measures has been to build a fish pass at the Geesthacht weir. This facility now ensures full passability of the dam, which is of particular benefit to anadromous fishes, more of which may now reach spawning grounds upstream of Geesthacht. The design of the fish pass not only takes the FFH species into account, but a wide range of different fishes, from European sturgeon as the largest autochthonous species, to small species such as stickleback and smelt. Considering the complex conditions at the site, a transdisciplinary planning team was established, which consistently made use of state of the art technology to facilitate the highest possible efficiency of the fish pass. The planning permission for the double slot fish pass was given on 16th October 2009. After 16 months of construction the fish pass went into operation in August 2010.

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